1. A mathematically precise statement of a system security policy. Some formal modeling techniques include: state transition models, temporal logic models, denotational semantics models, and algebraic specification models [POSIX.6]. 2. A mathematically precise statement of a security policy. To be adequately precise, such a model must represent the initial state of a system, the way in which the system progresses from one state to another, and a definition of a "secure" state of the system. To be acceptable as a basis for a TCB, the model must be supported by a formal proof that if the initial state of the system satisfies the definition of s "secure" state and if all assumptions required by the model hold, then all future states of the system will be secure. Some formal modeling techniques include: state transition models, temporal logic models, denotational semantics models, algebraic specification models. An example is the model described by Bell and LaPadula in reference [2] [TCSEC]. See also: Bell-LaPadula Model, Security Policy Model.